Abstract
A waterbody detection technique is an essential part of a digital elevation model (DEM) generation to delineate land–water boundaries and set flattened elevations. This paper describes the technical methodology for improving the initial tile-based waterbody data that are created during production of the Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER) GDEM, because without improvement such tile-based waterbodies data are not suitable for incorporating into the new ASTER GDEM Version 3. Waterbodies are classified into three categories: sea, lake, and river. For sea-waterbodies, the effect of sea ice is removed to better delineate sea shorelines in high latitude areas: sea ice prevents accurate delineation of sea shorelines. For lake-waterbodies, the major part of the processing is to set the unique elevation value for each lake using a mosaic image that covers the entire lake area. Rivers present a unique challenge, because their elevations gradually step down from upstream to downstream. Initially, visual inspection is required to separate rivers from lakes. A stepwise elevation assignment, with a step of one meter, is carried out by manual or automated methods, depending on the situation. The ASTER global water database (GWBD) product consists of a global set of 1° latitude-by-1° longitude tiles containing water body attribute and elevation data files in geographic latitude and longitude coordinates and with one arc second posting. Each tile contains 3601-by-3601 data points. All improved waterbody elevation data are incorporated into the ASTER GDEM to reflect the improved results.
Highlights
The Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER) is an advanced multispectral imaging sensor that was launched on board the Terra spacecraft in December, 1999 [1,2]
Lakes that cross tile boundaries and are situated in two adjacent 1◦ latitude-by-1◦ longitude tiles may have slightly different elevations in the two adjacent tiles. Another shortcoming of the ASTER GDEM Version 2 approach to waterbody detection and correction was that river elevations did not uniformly step-down from upstream to downstream
Target areas for sea ice removal were selected using the global coarse mosaic image that was generated from original ASTER GDEM data
Summary
The Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER) is an advanced multispectral imaging sensor that was launched on board the Terra spacecraft in December, 1999 [1,2]. Lakes that cross tile boundaries and are situated in two adjacent 1◦ latitude-by-1◦ longitude tiles may have slightly different elevations in the two adjacent tiles Another shortcoming of the ASTER GDEM Version 2 approach to waterbody detection and correction was that river elevations did not uniformly step-down from upstream to downstream. ASTER data and the ASTER GDEM cover land surface areas between 83◦ south 83◦ north latitudes, an important attribute in the generation of a global waterbody database. The new ASTER GWBD product consists of a global set of 1◦ latitude-by-1◦ longitude tiles that contain water body attribute and elevation data files in geographic latitude and longitude coordinates and with one arc-second postings. In addition to ASTER GDEM V3, the improved ASTER GWBD will be released to public sometime in 2018
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